I. Field of the Invention
The present invention relates generally to elongated support braces which are secured across a plurality of parallel joists in a wall structure to resist the tendency of the wall structure to rack under load, and more particularly, to such a brace which is embedded in aligned narrow channels cut transversely into the front surface of each of the plurality of parallel trusses.
II. Description of the Prior Art
Wall frames are typically constructed by securing a plurality of spaced and parallel vertically extending joists or trusses between horizontally extending beams called plates. Although the joists are secured to the plates, additional strengthening of the structure is necessary in order to resist the tendency of the structure to rack under load such as wind or seismic forces and to increase the load carrying capacity of the structure. Thus, a diagonally extending bracing member is often secured across the parallel joists in order to provide such additional support.
One previously known type of wall construction employed wooden brace members having a let-in construction. This let-in construction is formed by providing a plurality of aligned recesses within the parallel truss members and providing correspondingly spaced recesses in a wooden brace member. In this manner, the wooden brace extends across and between the parallel joists and is secured by fasteners such as nails to each of the joists. Such a construction is not only time consuming to cut and construct, but it also requires that the recesses be sufficiently deep to permit paneling or other surface material to be layed flat against the trusses of the wall structure. Moreover, the removal of sections of the trusses in order to form the appropriate recesses increases the infirmity of the completed structure. In addition, testing of these braces and wall construction indicate that when the wall begins to fail because of racking caused by application of an excessive load, the fasteners pull out of the frame members. Consequently, the brace is pulled apart from the wall structure, whereby the strength of the wall structure is decreased.
One previously known device used to overcome the disadvantages of let-in bracing is the T-shaped metal brace such as the braces disclosed in U.S. Pat. No. 3,875,719. The metal support strip is generally T-shaped with a narrow U-shaped portion forming the base leg of the T. The brace is secured across parallel wooden trusses or joists by embedding the base portion of the strip in aligned saw kerfs extending across the joists. The strips are commonly secured by fasteners such as nails to each of the joists which it crosses. While these previously known metal braces have been found to be advantageous over wood let-in construction, it has also been found that a large number of nails is required to secure the strip to the trusses and to insure that the base remains embedded in the saw kerfs. In addition, these previously known strips and wall constructions have not been designed with regard to the inertial characteristics of the strip about the major and minor axes of the T-shaped configuration. Consequently, the maximum strength and maximum strength per dimension have not previously been realized or utilized in T-shaped metal supports for wood structural elements. Moreover, they are inefficient because they do not make full use of the effects resulting from the connection to the joists.